Ofcom have made availabe a new site,
http://www.topcomm.org.uk which allows you to compare the largest telcos in the UK on a few key factors.
Service Provision - What % of services provisioned on time.
Reported Faults - How many faults per x lines.
Service Restoration - Length of time to fix these faults.
Complaints - Complaints handled within 28 days.
Billing Accuracy - How many justified billing complaints there are.
Comparing the 4 with their own infrastructure, BT, Kingston, Telewest and ntl gives some interesting results.
ntl are the worst for billing accuracy by a mile.
2nd to Kingston and just above BT for provision.
Worst fault rate, just ahead of BT and Telewest.
2nd best for fault resolution behind Kingston and just ahead of BT.
Worst by a fair distance for complaint handling, BT are next worst then Telewest.
Kingston were the best company in every catagory. Overall BT finish second, Telewest 3rd and ntl come in last place according to that website.
There's other companies to compare, have fun.